1. Field of the Invention
The present invention relates to a vertical-type heat treatment apparatus.
2. Description of the Related Art
During the manufacture of semiconductor devices, various types of heat treatment apparatuses are used to conduct oxidizing, diffusing, chemical vapor deposition (CVD), annealing, and/or other heat treatment processes, upon materials to be heat-treated, such as semiconductor wafers. Among these apparatuses is known a vertical-type heat treatment apparatus capable of heat-treating a large number of sheets at a time. This conventional vertical-type heat treatment apparatus includes a quartz-made treating vessel having an opening in its lower portion, a lid for blocking/unblocking the opening in the treating vessel, a holder provided on the lid, for holding in a vertical direction at predetermined spatial intervals, a plurality of objects to be processed, and a furnace body surrounding the treating vessel and including a heater to heat the target materials after loading of the materials into the treating vessel.
JP-A-2002-305189, for example, proposes another vertical-type heat treatment apparatus, which is equipped with an air blower to forcibly air-cool a treating vessel by supplying air to the inside of a furnace body including a heater. The blower has been used for rapidly cooling wafers and the treating vessel after heat treatment.
Heat treatment processes include heat-treating wafers in a low-temperature region of, for example, 100 to 500° C., for a purpose such as forming a layer of a low dielectric constant. During the heat treatment in the low-temperature region, it becomes important how fast the furnace interior can be heated up or cooled down to a predetermined heat-treating temperature. An existing heat-treatment apparatus proposed for low-temperature applications includes a metallic treating chamber, not a quartz-made treating vessel, to obtain faster thermal response. However, if reaction products, by-products, or other substances are likely to stick to the furnace interior during the heat treatment, the use of a quartz-made treating vessel easier to clean and replace than a metallic treating chamber is necessary for reasons associated with the apparatus configuration. Additionally, although energy saving in the apparatus is achievable by using a heater having high heat-insulating performance, the use of the heater deteriorates the furnace in the controllability of internal temperature. In this case, it also becomes important how fast the furnace interior can be heated up or cooled down to a predetermined heat-treating temperature, and this issue also applies to temperatures other than those of the low-temperature region discussed above.